Mercedes-Benz CLR
The Mercedes-Benz CLR was a prototype race car developed by Mercedes-Benz in collaboration with in-house tuning division AMG and motorsports specialists HWA GmbH. Designed to meet Le Mans Grand Touring Prototype regulations, the CLRs were intended to compete in sports car events during 1999, most notably at the 24 Hours of Le Mans which Mercedes had last won in. It was the third iteration in Mercedes' 1990s sports cars, succeeding the Mercedes-Benz CLK LM, which in turn was born of the CLK GTR. Similar to its predecessors, CLR retained elements of Mercedes-Benz's production cars, including a V8 engine loosely based on the Mercedes M119 as well as a front fascia, headlamps, and grille inspired by the then new Mercedes flagship CL Class.
Three CLRs were entered for Le Mans in 1999 after the team performed nearly of testing. The cars suffered aerodynamic instabilities along the circuit's long high-speed straight sections. The car of Australian Mark Webber became airborne and crashed in qualifying, requiring it to be rebuilt. Webber and the repaired CLR returned to the track in a final practice session on the morning of the race, but during its first lap around the circuit, the car once again became airborne and landed on its roof. Mercedes withdrew the damaged CLR but chose to continue in the race despite the accidents. The remaining cars were hastily altered and the drivers were given instructions to avoid closely following other cars.
Nearly four hours into the race, Scotsman Peter Dumbreck was battling amongst the race leaders when his CLR suffered the same instability and became airborne, this time vaulting the circuit's safety barriers, crashing into trees and then coming to rest in an open field after several somersaults. This and earlier incidents led Mercedes not only to withdraw its remaining car from the event immediately, but also to cancel the entire CLR programme and move the company out of sports car racing. The accidents led to changes in the regulations dictating the design of Le Mans racing cars as well as alterations to the circuit itself to increase safety.
Background
In 1996 Mercedes-Benz's motorsports programmes included support for cars in Formula One, IndyCar, and the International Touring Car Championship. Following the collapse of the ITC at the end of the 1996 season, Mercedes' attention shifted to a new international series, the FIA GT Championship. Racing partners AMG were tasked with developing a design to meet the Fédération Internationale de l'Automobile's GT1 regulations for the new championship. The new cars, known as CLK GTRs, were designed for use both as racing and road cars available to the public, as series regulations required the racing cars to be based on production models. The CLK GTRs were successful in their debut season, winning seven of eleven races and earning both the drivers' and teams' championships.For the 1998 season AMG refined the CLK GTR's design with the launch of the new CLK LM. A major change for the new design was the replacement of the CLK GTR's V12 engine with a smaller V8, thought by Mercedes to be more suitable to take on longer endurance events such as the 24 Hours of Le Mans, a race not part of the FIA GT calendar. Despite earning pole position for Le Mans, the new cars were unreliable and both lasted less than three hours before retiring with mechanical failure. The race was won by Mercedes' FIA GT rivals Porsche. Mercedes did go on to win its second straight FIA GT Championships later that year after winning all ten races.
After the dominance of Mercedes, most of the GT1 class competitors chose to not return to the FIA GT Championship for 1999, leading the FIA to eliminate the category from the series. The Automobile Club de l'Ouest, organisers of the 24 Hours of Le Mans, chose to follow the FIA's lead and no longer allow GT1 category cars to enter Le Mans. While FIA GT concentrated solely on its lower GT2 category in 1999, the ACO created a new category of race car known as a Le Mans Grand Touring Prototype. The LMGTP regulations for closed-cockpit cars were similar to the former GT1 regulations but shared many elements with the ACO's existing open-cockpit Le Mans Prototype category. Mercedes, no longer able to compete in the FIA GT Championship with the CLK LMs, chose to concentrate on the ACO's new LMGTP category.
Development
Work on designing a new car to meet LMGTP regulations began in September 1998 as Mercedes was closing out its second FIA GT Championship season. Development was led by HWA GmbH, the motorsports division of AMG, which became an independent company the following year. The LMGTP rules did not require road versions of the cars to be built, so Gerhard Ungar, chief designer for HWA, was free to develop the CLR without concern for road legality issues or the inclusion of driver comforts. The transition from GT1 to LMGTP also allowed a decrease in the minimum allowed weight, from to. The new design had a much smaller cockpit monocoque made from carbon fibre and aluminium honeycomb. The monocoque derived the design of its lower half from the CLK LM's combination of carbon fibre and steel tube frame, but required a full carbon and aluminium upper half because of new load tests mandatory for LMGTP cockpits. The bodywork of the CLR was also shorter in overall height compared to the CLK LM, while the nose was substantially lower and flatter than its predecessor due to a shorter wheelbase allowing longer overhangs. Aerodynamic development on the design was carried out at the University of Stuttgart's wind tunnel and assisted by the aerodynamic specialists Fondmetal Technologies. Aerodynamic emphasis was placed on low drag for maximum top speed. Mercedes-Benz's brand image was also retained with the reuse of CLK-Class styled tail lights from the CLK LM and a front fascia, grille and headlamps based on the then-new CL-Class.The engine for the CLR was also a variant of the design used on the CLK LM. The GT108C 32 valve naturally aspirated V8 engine was loosely based on the M119 engine used in Mercedes-Benz road cars at that time. A previous variant of the M119 had won Le Mans for Mercedes in 1989. Displacement was increased from to to compensate for the new air restrictor limitations in the LMGTP category, which allowed the engine to produce approximately. The first engine was completed and began testing in December 1998. The Xtrac 6-speed sequential gearbox came directly from the CLK LM, while Bridgestone continued as the team's tyre supplier. The suspension setup from the CLK LM was largely carried over to the CLR, although a central spring was added to the rear suspension.
Mercedes publicly announced its CLR programme in February 1999 just days before the first car began private testing at California Speedway in the United States. Testing continued into March at California as well as Homestead-Miami Speedway in Florida before the team moved to the Circuit de Nevers Magny-Cours in France. At Magny-Cours three CLRs completed a 30-hour test session covering. On 20 April the CLR was shown to the press for the first time during a test session at the Hockenheimring in Germany. By that point in the development process the CLRs had covered in testing without any major failures.
Preparation
The initial schedule for the CLRs consisted of participation in the May pre-qualifying and testing session at Le Mans in preparation for the race in June. At the team's Hockenheim test session plans were announced to enter several races after Le Mans. The first, scheduled for July, was to be an exhibition event consisting of two races at the Norisring street circuit in Nuremberg, Germany. Mercedes planned to enter four CLRs in the event. The team would then end its season with the final three races of the American Le Mans Series: the 10-hour Petit Le Mans endurance at Road Atlanta and shorter races at Laguna Seca Raceway and Las Vegas Motor Speedway. More than 200 personnel from Mercedes-Benz and HWA formed the crew for the three cars although the team was officially known as AMG-Mercedes.As part of its launch announcement in February 1999, Mercedes named nine drivers to the team. Retained from the FIA GT programme were Christophe Bouchut, Jean-Marc Gounon, Bernd Schneider, Marcel Tiemann, and Mark Webber. Nick Heidfeld, then a test driver for the McLaren Mercedes Formula One team, was added to the team for his first experience with sports cars. Former Macau Grand Prix winner and All-Japan Formula Three champion Peter Dumbreck also came from an open wheel racing background. Pedro Lamy, 1998 FIA GT2 Champion, was drafted from the Oreca Chrysler team to participate at Le Mans and in the Deutsche Tourewagen Masters for Mercedes, while Franck Lagorce transferred from Nissan's Le Mans squad. Darren Turner, also a test driver for McLaren, served as the team's reserve driver for Le Mans.
Le Mans
Practice and qualifying
By winning the 1998 FIA GT Championship, Mercedes were awarded a single guaranteed entry for Le Mans, which was assigned to Gounon, Tiemann, and Webber in CLR No. 4. Bouchut, Dumbreck, and Heidfeld in the No. 5 and Lagorce, Lamy, and Schneider in the No. 6 entries would have to pre-qualify for the event, while No. 4 was free to use the pre-qualifying session for testing purposes. Pre-qualifying involved all 62 entry applicant teams setting lap times over a long session. The final entry for Le Mans would be made of 48 cars, combining guaranteed entries and the fastest cars in pre-qualifying within their respective classes; the prototype category, combining LMP and LMGTP cars, only allowed 28 cars from 31 entries. Competitors in the prototype category for 1999 included factory-supported LMGTP programmes from Toyota and Audi, and LMP entries from Nissan, BMW, Audi, and Panoz. Toyota set the fastest pre-qualifying time overall, followed by Panoz and BMW. Mercedes No. 6 was the sixth fastest car, while Nos. 4 and 5 were 14th and 15th respectively. Although the cars succeeded in passing pre-qualifying, one CLR suffered a setback when a suspension linkage was torn from the front of the monocoque. The suspension failure was the first major fault suffered by the CLRs since their testing debut in February.Several weeks after pre-qualifying, Mercedes' returned for two days of practice and qualifying sessions in the week leading up to the race. The sessions would set the starting grid for the race based on the fastest overall lap time by each car. At the end of the first day, Mercedes' entries were fifth, sixth, and eighth on the provisional grid. Toyota led the session, over four seconds ahead of the fastest Mercedes. Early in the second day of sessions, Webber, driving CLR No. 4, was following the Audi R8R of Frank Biela through the portion of the circuit connecting Mulsanne Corner and the Indianapolis complex when he moved out of the Audi's slipstream to overtake. The CLR suddenly lifted its nose and front wheels off the circuit and became airborne, flipping upwards and somersaulting backwards before rotating onto its side. The car impacted the tarmac with its right side while perpendicular to the circuit then flipped back onto its wheels before skidding into the safety barriers on the side of the circuit. Webber was extracted from the car by track marshals and taken to a nearby hospital suffering from a sore neck, chest, and back. The accident occurred in an area not generally accessible to the public and was not seen by television cameras.
Due to the accident, the No. 4 car was unable to improve its qualifying time from the previous day, which relegated the car to tenth on the starting grid as competitors improved their times; Mercedes No. 5 also did not improve its lap time and finished the session seventh. Bernd Schneider was able to go quicker than his time from the previous day with a 3:31.541 lap for the No. 6 car. Toyota took pole position with a 3:29.930 lap, while Schneider's car was placed fourth on the final starting grid. The wreckage of the CLR No. 4 was returned to Mercedes at the end of the qualifying session and the team issued a press release confirming that they could repair the car before the start of the race two days later. A spare CLR monocoque, taken from a test car, was used to rebuild the No. 4. Webber was able to recover from his injuries by spending the following day in physical training and was cleared on Saturday morning to participate in the race.